Signaling output picture size for reference picture resampling

ABSTRACT

There is included a method and apparatus comprising computer code configured to cause a processor or processors to perform acquiring an input bitstream comprising metadata and video data, decoding the video data, determining whether the metadata comprises at least one flag signaling at least one component of a picture size of at least one picture of the video data, and signaling, in a case where it is determined that the metadata comprises the at least one flag, a display device to display the at least one picture from the video data according to the at least one flag.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a Continuation Application of U.S.application Ser. No. 17/063,253 filed on Oct. 5, 2020, which claimspriority to provisional application U.S. 62/955,514 filed on Dec. 31,2019 which are hereby expressly incorporated by reference, in theirentireties, into the present application.

BACKGROUND 1. Field

The present disclosure is directed to signaling constant picture sizeinformation, for example in video usage information (VUI), whereaccording to exemplary embodiments, such information may indicate, amongother information described herein, a guided output picture size fordisplay, any of with and without one or more cropped output pictureshaving any of one or more different width and height values with respectto processing such as reference picture resampling (RPR).

2. Description of Related Art

In the versatile video coding (VVC) specification draft JVET-P2001(editorially updated by JVET-Q0041), an RPR may enable a change of oneor more decoded picture spatial resolutions. Depending on a picturewidth and height and cropping window offset values signaled in a pictureparameter set (PPS), each output picture may have a different picturesize than other output pictures. However, such features aredisadvantageously dependent on requiring that a display device, as postprocessing for example, has a capability to rescale the output picturesto a constant picture size to be fit into the display device displayresolution.

Such post processing has been disadvantageously purely the role of eachdisplay device and therefore limits, technically, capabilities forpre-processing control of output display, such as display device displayresolution, at the display device. For example, in some content servicescenarios, a content provider may be prevented, by technicallimitations, from having provided video content consumed, or at leastoutput, by a specific resolution, and further may even be prevented fromeven indicating the best or recommended resolution for display, inaccordance with, for example, a director's intention.

Further, even JVET-N0052 rejected signaling the (constant) outputpicture size in SPS, to leave such process or processes, as a postprocessing, out of decoding process.

Therefore, there is a desire for a technical solution to such problems.

SUMMARY

To address one or more different requirements, which are carrying anintention, such as a director's intention, and leaving a freedom of adisplay for post processing, the inventors herein disclose technicalsolutions including signaling any of a constant output picture size inVUI, for example as an informative metadata. According to embodiments,an end user's device may still have a freedom to choose the displaypicture resolution, while also being able to accept a director'ssuggestion, optionally.

There is included a method and apparatus comprising memory configured tostore computer program code and a processor or processors configured toaccess the computer program code and operate as instructed by thecomputer program code. The computer program code includes acquiring codeconfigured to cause the at least one processor to acquire an inputbitstream comprising metadata and video data, decoding code configuredto cause the at least one processor to decode the video data,determining code configured to cause the at least one processor todetermine whether the metadata comprises at least one flag signaling atleast one component of a picture size of at least one picture of thevideo data, and signaling code configured to cause the at least oneprocessor to signal, in a case where it is determined that the metadatacomprises the at least one flag, a display device to display the atleast one picture from the video data according to the at least oneflag.

According to exemplary embodiments, the video data is encoded in aversatile video coding (VVC) format.

According to exemplary embodiments, the at least one flag specifieswhether to display the at least one picture at the picture sizeaccording to a value of the component that is preset and indicated bythe metadata.

According to exemplary embodiments, the component comprises at least oneof a width and a height of the at least one picture.

According to exemplary embodiments, the at least one of the width andthe height of the at least one picture comprises units of luma samples.

According to exemplary embodiments, the determining code is furtherconfigured to cause the at least one processor to determine, in responseto determining that the metadata comprises the at least one flag,whether the metadata comprises a width value specifying the width withrespect to a plurality of pictures, including the at least one picture,and whether the metadata comprises a height value specifying the heightwith respect to the plurality of pictures, and according to exemplaryembodiments, at least one of the value of the component comprises atleast one of the width and the height.

According to exemplary embodiments, the signaling code is furtherconfigured to cause the at least one processor to signal, in response todetermining that the metadata comprises at least one of the width valueand the height value, at least one post-resampling process to maintainthe at least one of the width value and the height value for display ofthe at least one picture by the display device.

According to exemplary embodiments, the signaling code is furtherconfigured to cause the at least one processor to signal, in response todetermining that the metadata is absent the width value, the at leastone post-resampling process to maintain the width value at a heightindicated by a sequence parameter set of the video data.

According to exemplary embodiments, the signaling code is furtherconfigured to cause the at least one processor to signal, in response todetermining that the metadata is absent the height value, the at leastone post-resampling process to maintain the height value at a heightindicated by a sequence parameter set of the video data.

According to exemplary embodiments, the video data comprises the atleast one flag as a video usage information (VUI) parameter.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIGS. 1-9B are schematic illustrations of diagrams in accordance withembodiments.

FIG. 10 is a simplified block diagram in accordance with embodiments.

FIG. 11 is a simplified illustration in accordance with embodiments.

FIG. 12 is a schematic illustration of a diagram in accordance withembodiments.

DETAILED DESCRIPTION

The proposed features discussed below may be used separately or combinedin any order. Further, the embodiments may be implemented by processingcircuitry (e.g., one or more processors or one or more integratedcircuits). In one example, the one or more processors execute a programthat is stored in a non-transitory computer-readable medium.

FIG. 1 illustrates a simplified block diagram of a communication system100 according to an embodiment of the present disclosure. Thecommunication system 100 may include at least two terminals 102 and 103interconnected via a network 105. For unidirectional transmission ofdata, a first terminal 103 may code video data at a local location fortransmission to the other terminal 102 via the network 105. The secondterminal 102 may receive the coded video data of the other terminal fromthe network 105, decode the coded data and display the recovered videodata. Unidirectional data transmission may be common in media servingapplications and the like.

FIG. 1 illustrates a second pair of terminals 101 and 104 provided tosupport bidirectional transmission of coded video that may occur, forexample, during videoconferencing. For bidirectional transmission ofdata, each terminal 101 and 104 may code video data captured at a locallocation for transmission to the other terminal via the network 105.Each terminal 101 and 104 also may receive the coded video datatransmitted by the other terminal, may decode the coded data and maydisplay the recovered video data at a local display device.

In FIG. 1 , the terminals 101, 102, 103 and 104 may be illustrated asservers, personal computers and smart phones but the principles of thepresent disclosure are not so limited. Embodiments of the presentdisclosure find application with laptop computers, tablet computers,media players and/or dedicated video conferencing equipment. The network105 represents any number of networks that convey coded video data amongthe terminals 101, 102, 103 and 104, including for example wirelineand/or wireless communication networks. The communication network 105may exchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network 105may be immaterial to the operation of the present disclosure unlessexplained herein below.

FIG. 2 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and decoder in astreaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem 203, that can includea video source 201, for example a digital camera, creating, for example,an uncompressed video sample stream 213. That sample stream 213 may beemphasized as a high data volume when compared to encoded videobitstreams and can be processed by an encoder 202 coupled to the camera201. The encoder 202 can include hardware, software, or a combinationthereof to enable or implement aspects of the disclosed subject matteras described in more detail below. The encoded video bitstream 204,which may be emphasized as a lower data volume when compared to thesample stream, can be stored on a streaming server 205 for future use.One or more streaming clients 212 and 207 can access the streamingserver 205 to retrieve copies 208 and 206 of the encoded video bitstream204. A client 212 can include a video decoder 211 which decodes theincoming copy of the encoded video bitstream 208 and creates an outgoingvideo sample stream 210 that can be rendered on a display 209 or otherrendering device (not depicted). In some streaming systems, the videobitstreams 204, 206 and 208 can be encoded according to certain videocoding/compression standards. Examples of those standards are notedabove and described further herein.

FIG. 3 may be a functional block diagram of a video decoder 300according to an embodiment of the present invention.

A receiver 302 may receive one or more codec video sequences to bedecoded by the decoder 300; in the same or another embodiment, one codedvideo sequence at a time, where the decoding of each coded videosequence is independent from other coded video sequences. The codedvideo sequence may be received from a channel 301, which may be ahardware/software link to a storage device which stores the encodedvideo data. The receiver 302 may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver 302 may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory 303 may be coupled inbetween receiver 302 and entropy decoder/parser 304 (“parser”henceforth). When receiver 302 is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosychronous network, the buffer 303 may not be needed, or can besmall. For use on best effort packet networks such as the Internet, thebuffer 303 may be required, can be comparatively large and canadvantageously of adaptive size.

The video decoder 300 may include a parser 304 to reconstruct symbols313 from the entropy coded video sequence. Categories of those symbolsinclude information used to manage operation of the decoder 300, andpotentially information to control a rendering device such as a display312 that is not an integral part of the decoder but can be coupled toit. The control information for the rendering device(s) may be in theform of Supplementary Enhancement Information (SEI messages) or VideoUsability Information parameter set fragments (not depicted). The parser304 may parse/entropy-decode the coded video sequence received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow principles well known to aperson skilled in the art, including variable length coding, Huffmancoding, arithmetic coding with or without context sensitivity, and soforth. The parser 304 may extract from the coded video sequence, a setof subgroup parameters for at least one of the subgroups of pixels inthe video decoder, based upon at least one parameters corresponding tothe group. Subgroups can include Groups of Pictures (GOPs), pictures,tiles, slices, macroblocks, Coding Units (CUs), blocks, Transform Units(TUs), Prediction Units (PUs) and so forth. The entropy decoder/parsermay also extract from the coded video sequence information such astransform coefficients, quantizer parameter values, motion vectors, andso forth.

The parser 304 may perform entropy decoding/parsing operation on thevideo sequence received from the buffer 303, so to create symbols 313.The parser 304 may receive encoded data, and selectively decodeparticular symbols 313. Further, the parser 304 may determine whetherthe particular symbols 313 are to be provided to a Motion CompensationPrediction unit 306, a scaler/inverse transform unit 305, an IntraPrediction Unit 307, or a loop filter 311.

Reconstruction of the symbols 313 can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser 304. The flow of such subgroup control information between theparser 304 and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, decoder 300 can beconceptually subdivided into a number of functional units as describedbelow. In a practical implementation operating under commercialconstraints, many of these units interact closely with each other andcan, at least partly, be integrated into each other. However, for thepurpose of describing the disclosed subject matter, the conceptualsubdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit 305. Thescaler/inverse transform unit 305 receives quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) 313 from the parser 304. It can output blockscomprising sample values, that can be input into aggregator 310.

In some cases, the output samples of the scaler/inverse transform 305can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit 307. In some cases, the intra picture predictionunit 307 generates a block of the same size and shape of the block underreconstruction, using surrounding already reconstructed informationfetched from the current (partly reconstructed) picture 309. Theaggregator 310, in some cases, adds, on a per sample basis, theprediction information the intra prediction unit 307 has generated tothe output sample information as provided by the scaler/inversetransform unit 305.

In other cases, the output samples of the scaler/inverse transform unit305 can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a Motion Compensation Prediction unit 306 canaccess reference picture memory 308 to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols 313 pertaining to the block, these samples can be addedby the aggregator 310 to the output of the scaler/inverse transform unit(in this case called the residual samples or residual signal) so togenerate output sample information. The addresses within the referencepicture memory form where the motion compensation unit fetchesprediction samples can be controlled by motion vectors, available to themotion compensation unit in the form of symbols 313 that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory when sub-sample exact motion vectors are in use, motionvector prediction mechanisms, and so forth.

The output samples of the aggregator 310 can be subject to various loopfiltering techniques in the loop filter unit 311. Video compressiontechnologies can include in-loop filter technologies that are controlledby parameters included in the coded video bitstream and made availableto the loop filter unit 311 as symbols 313 from the parser 304, but canalso be responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit 311 can be a sample stream that canbe output to the render device 312 as well as stored in the referencepicture memory 557 for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. Once a coded picture is fullyreconstructed and the coded picture has been identified as a referencepicture (by, for example, parser 304), the current reference picture 309can become part of the reference picture buffer 308, and a fresh currentpicture memory can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder 300 may perform decoding operations according to apredetermined video compression technology that may be documented in astandard, such as ITU-T Rec. H.265. The coded video sequence may conformto a syntax specified by the video compression technology or standardbeing used, in the sense that it adheres to the syntax of the videocompression technology or standard, as specified in the videocompression technology document or standard and specifically in theprofiles document therein. Also necessary for compliance can be that thecomplexity of the coded video sequence is within bounds as defined bythe level of the video compression technology or standard. In somecases, levels restrict the maximum picture size, maximum frame rate,maximum reconstruction sample rate (measured in, for example megasamplesper second), maximum reference picture size, and so on. Limits set bylevels can, in some cases, be further restricted through HypotheticalReference Decoder (HRD) specifications and metadata for HRD buffermanagement signaled in the coded video sequence.

In an embodiment, the receiver 302 may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder 300 to properly decode the data and/or to more accuratelyreconstruct the original video data. Additional data can be in the formof, for example, temporal, spatial, or signal-to-noise ratio (SNR)enhancement layers, redundant slices, redundant pictures, forward errorcorrection codes, and so on.

FIG. 4 may be a functional block diagram of a video encoder 400according to an embodiment of the present disclosure.

The encoder 400 may receive video samples from a video source 401 (thatis not part of the encoder) that may capture video image(s) to be codedby the encoder 400.

The video source 401 may provide the source video sequence to be codedby the encoder (303) in the form of a digital video sample stream thatcan be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, .. . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ) and anysuitable sampling structure (for example Y CrCb 4:2:0, Y CrCb 4:4:4). Ina media serving system, the video source 401 may be a storage devicestoring previously prepared video. In a videoconferencing system, thevideo source 401 may be a camera that captures local image informationas a video sequence. Video data may be provided as a plurality ofindividual pictures that impart motion when viewed in sequence. Thepictures themselves may be organized as a spatial array of pixels,wherein each pixel can comprise one or more samples depending on thesampling structure, color space, etc. in use. A person skilled in theart can readily understand the relationship between pixels and samples.The description below focuses on samples.

According to an embodiment, the encoder 400 may code and compress thepictures of the source video sequence into a coded video sequence 410 inreal time or under any other time constraints as required by theapplication. Enforcing appropriate coding speed is one function ofController 402. Controller controls other functional units as describedbelow and is functionally coupled to these units. The coupling is notdepicted for clarity. Parameters set by controller can include ratecontrol related parameters (picture skip, quantizer, lambda value ofrate-distortion optimization techniques, . . . ), picture size, group ofpictures (GOP) layout, maximum motion vector search range, and so forth.A person skilled in the art can readily identify other functions ofcontroller 402 as they may pertain to video encoder 400 optimized for acertain system design.

Some video encoders operate in what a person skilled in the art readilyrecognizes as a “coding loop.” As an oversimplified description, acoding loop can consist of the encoding part of an encoder 402 (“sourcecoder” henceforth) (responsible for creating symbols based on an inputpicture to be coded, and a reference picture(s)), and a (local) decoder406 embedded in the encoder 400 that reconstructs the symbols to createthe sample data that a (remote) decoder also would create (as anycompression between symbols and coded video bitstream is lossless in thevideo compression technologies considered in the disclosed subjectmatter). That reconstructed sample stream is input to the referencepicture memory 405. As the decoding of a symbol stream leads tobit-exact results independent of decoder location (local or remote), thereference picture buffer content is also bit exact between local encoderand remote encoder. In other words, the prediction part of an encoder“sees” as reference picture samples exactly the same sample values as adecoder would “see” when using prediction during decoding. Thisfundamental principle of reference picture synchronicity (and resultingdrift, if synchronicity cannot be maintained, for example because ofchannel errors) is well known to a person skilled in the art.

The operation of the “local” decoder 406 can be the same as of a“remote” decoder 300, which has already been described in detail abovein conjunction with FIG. 3 . Briefly referring also to FIG. 4 , however,as symbols are available and en/decoding of symbols to a coded videosequence by entropy coder 408 and parser 304 can be lossless, theentropy decoding parts of decoder 300, including channel 301, receiver302, buffer 303, and parser 304 may not be fully implemented in localdecoder 406.

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. The description of encodertechnologies can be abbreviated as they are the inverse of thecomprehensively described decoder technologies. Only in certain areas amore detail description is required and provided below.

As part of its operation, the source coder 403 may perform motioncompensated predictive coding, which codes an input frame predictivelywith reference to one or more previously-coded frames from the videosequence that were designated as “reference frames.” In this manner, thecoding engine 407 codes differences between pixel blocks of an inputframe and pixel blocks of reference frame(s) that may be selected asprediction reference(s) to the input frame.

The local video decoder 406 may decode coded video data of frames thatmay be designated as reference frames, based on symbols created by thesource coder 403. Operations of the coding engine 407 may advantageouslybe lossy processes. When the coded video data may be decoded at a videodecoder (not shown in FIG. 4 ), the reconstructed video sequencetypically may be a replica of the source video sequence with someerrors. The local video decoder 406 replicates decoding processes thatmay be performed by the video decoder on reference frames and may causereconstructed reference frames to be stored in the reference picturecache 405. In this manner, the encoder 400 may store copies ofreconstructed reference frames locally that have common content as thereconstructed reference frames that will be obtained by a far-end videodecoder (absent transmission errors).

The predictor 404 may perform prediction searches for the coding engine407. That is, for a new frame to be coded, the predictor 404 may searchthe reference picture memory 405 for sample data (as candidate referencepixel blocks) or certain metadata such as reference picture motionvectors, block shapes, and so on, that may serve as an appropriateprediction reference for the new pictures. The predictor 404 may operateon a sample block-by-pixel block basis to find appropriate predictionreferences. In some cases, as determined by search results obtained bythe predictor 404, an input picture may have prediction references drawnfrom multiple reference pictures stored in the reference picture memory405.

The controller 402 may manage coding operations of the video coder 403,including, for example, setting of parameters and subgroup parametersused for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder 408. The entropy coder translatesthe symbols as generated by the various functional units into a codedvideo sequence, by loss-less compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter 409 may buffer the coded video sequence(s) as created bythe entropy coder 408 to prepare it for transmission via a communicationchannel 411, which may be a hardware/software link to a storage devicewhich would store the encoded video data. The transmitter 409 may mergecoded video data from the video coder 403 with other data to betransmitted, for example, coded audio data and/or ancillary data streams(sources not shown).

The controller 402 may manage operation of the encoder 400. Duringcoding, the controller 405 may assign to each coded picture a certaincoded picture type, which may affect the coding techniques that may beapplied to the respective picture. For example, pictures often may beassigned as one of the following frame types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other frame in the sequence as a source of prediction.Some video codecs allow for different types of Intra pictures,including, for example Independent Decoder Refresh Pictures. A personskilled in the art is aware of those variants of I pictures and theirrespective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded non-predictively,via spatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codednon-predictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video coder 400 may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video coder 400 may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter 409 may transmit additional data withthe encoded video. The source coder 403 may include such data as part ofthe coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

FIG. 5 illustrates intra prediction modes used in HEVC and JEM. Tocapture the arbitrary edge directions presented in natural video, thenumber of directional intra modes is extended from 33, as used in HEVC,to 65. The additional directional modes in JEM on top of HEVC aredepicted as dotted arrows in FIG. 1 (b), and the planar and DC modesremain the same. These denser directional intra prediction modes applyfor all block sizes and for both luma and chroma intra predictions. Asshown in FIG. 5 , the directional intra prediction modes as identifiedby dotted arrows, which is associated with an odd intra prediction modeindex, are called odd intra prediction modes. The directional intraprediction modes as identified by solid arrows, which are associatedwith an even intra prediction mode index, are called even intraprediction modes. In this document, the directional intra predictionmodes, as indicated by solid or dotted arrows in FIG. 5 are alsoreferred as angular modes.

In JEM, a total of 67 intra prediction modes are used for luma intraprediction. To code an intra mode, an most probable mode (MPM) list ofsize 6 is built based on the intra modes of the neighboring blocks. Ifintra mode is not from the MPM list, a flag is signaled to indicatewhether intra mode belongs to the selected modes. In JEM-3.0, there are16 selected modes, which are chosen uniformly as every fourth angularmode. In JVET-D0114 and JVET-G0060, 16 secondary MPMs are derived toreplace the uniformly selected modes.

FIG. 6 illustrates N reference tiers exploited for intra directionalmodes. There is a block unit 611, a segment A 601, a segment B 602, asegment C 603, a segment D 604, a segment E 605, a segment F 606, afirst reference tier 610, a second reference tier 609, a third referencetier 608 and a fourth reference tier 607.

In both HEVC and JEM, as well as some other standards such as H.264/AVC,the reference samples used for predicting the current block arerestricted to a nearest reference line (row or column). In the method ofmultiple reference line intra prediction, the number of candidatereference lines (row or columns) are increased from one (i.e. thenearest) to N for the intra directional modes, where N is an integergreater than or equal to one. FIG. 2 takes 4×4 prediction unit (PU) asan example to show the concept of the multiple line intra directionalprediction method. An intra-directional mode could arbitrarily chooseone of N reference tiers to generate the predictors. In other words, thepredictor p(x,y) is generated from one of the reference samples S1, S2,. . . , and SN. A flag is signaled to indicate which reference tier ischosen for an intra-directional mode. If N is set as 1, the intradirectional prediction method is the same as the traditional method inJEM 2.0. In FIG. 6 , the reference lines 610, 609, 608 and 607 arecomposed of six segments 601, 602, 603, 604, 605 and 606 together withthe top-left reference sample. In this document, a reference tier isalso called a reference line. The coordinate of the top-left pixelwithin current block unit is (0,0) and the top left pixel in the 1streference line is (−1,−1).

In JEM, for the luma component, the neighboring samples used for intraprediction sample generations are filtered before the generationprocess. The filtering is controlled by the given intra prediction modeand transform block size. If the intra prediction mode is DC or thetransform block size is equal to 4×4, neighboring samples are notfiltered. If the distance between the given intra prediction mode andvertical mode (or horizontal mode) is larger than predefined threshold,the filtering process is enabled. For neighboring sample filtering, [1,2, 1] filter and bi-linear filters are used.

A position dependent intra prediction combination (PDPC) method is anintra prediction method which invokes a combination of the un-filteredboundary reference samples and HEVC style intra prediction with filteredboundary reference samples. Each prediction sample pred[x][y] located at(x, y) is calculated as follows:

pred[x][y]=(wL*R_(-1,y)+wT*R_(x,-1)+wTL*R_(-1,-1)+(64−wL−wT−wTL)*pred[x][y]+32)>>6  (Eq. 2-1)

where R_(x,-1), R_(-1,y) represent the unfiltered reference sampleslocated at top and left of current sample (x, y), respectively, andR_(-1,-1) represents the unfiltered reference sample located at thetop-left corner of the current block. The weightings are calculated asbelow,

wT=32>>((y<<1)>>shift)   (Eq. 2-2)

wL=32>>((x<<1)>>shift)   (Eq. 2-3)

wTL=−(wL>>4)−(wT>>4)   (Eq. 2-4)

shift=(log2(width)+log2(height)+2)>>2   (Eq. 2-5).

FIG. 7 illustrates a diagram 700 in which DC mode PDPC weights (wL, wT,wTL) for (0, 0) and (1, 0) positions inside one 4×4 block. If PDPC isapplied to DC, planar, horizontal, and vertical intra modes, additionalboundary filters are not needed, such as the HEVC DC mode boundaryfilter or horizontal/vertical mode edge filters. FIG. 7 illustrates thedefinition of reference samples Rx,−1, R−1,y and R−1,−1 for PDPC appliedto the top-right diagonal mode. The prediction sample pred(x′, y′) islocated at (x′, y′) within the prediction block. The coordinate x of thereference sample Rx,−1 is given by: x=x′+y′+1, and the coordinate y ofthe reference sample R−1,y is similarly given by: y=x′+y′+1.

FIG. 8 illustrates a Local Illumination Compensation (LIC) diagram 800and is based on a linear model for illumination changes, using a scalingfactor a and an offset b. And it is enabled or disabled adaptively foreach inter-mode coded coding unit (CU).

When LIC applies for a CU, a least square error method is employed toderive the parameters a and b by using the neighboring samples of thecurrent CU and their corresponding reference samples. More specifically,as illustrated in FIG. 8 , the subsampled (2:1 subsampling) neighboringsamples of the CU and the corresponding samples (identified by motioninformation of the current CU or sub-CU) in the reference picture areused. The IC parameters are derived and applied for each predictiondirection separately.

When a CU is coded with merge mode, the LIC flag is copied fromneighboring blocks, in a way similar to motion information copy in mergemode; otherwise, an LIC flag is signaled for the CU to indicate whetherLIC applies or not.

FIG. 9A illustrates intra prediction modes 900 used in HEVC. In HEVC,there are total 35 intra prediction modes, among which mode 10 ishorizontal mode, mode 26 is vertical mode, and mode 2, mode 18 and mode34 are diagonal modes. The intra prediction modes are signaled by threemost probable modes (MPMs) and 32 remaining modes.

FIG. 9B illustrates, in embodiments of VVC, there are total 87 intraprediction modes where mode 18 is horizontal mode, mode 50 is verticalmode, and mode 2, mode 34 and mode 66 are diagonal modes. Modes −1˜−10and Modes 67˜76 are called Wide-Angle Intra Prediction (WAIP) modes.

The prediction sample pred(x,y) located at position (x, y) is predictedusing an intra prediction mode (DC, planar, angular) and a linearcombination of reference samples according to the PDPC expression:

pred(x,y)=(wL×R−1,y+wT×Rx,−1−wTL×R−1,−1+(64−wL−wT+wTL)×pred(x,y)+32)>>6

where Rx,−1, R−1,y represent the reference samples located at the topand left of current sample (x, y), respectively, and R−1,−1 representsthe reference sample located at the top-left corner of the currentblock.

For the DC mode the weights are calculated as follows for a block withdimensions width and height:

wT=32>>((y<<1)>>nScale), wL=32>>((x<<1)>>nScale), wTL=(wL>>4)+(wT>>4),

with nScale=(log2(width)−2+log2(height)−2+2)>>2, where wT denotes theweighting factor for the reference sample located in the above referenceline with the same horizontal coordinate, wL denotes the weightingfactor for the reference sample located in the left reference line withthe same vertical coordinate, and wTL denotes the weighting factor forthe top-left reference sample of the current block, nScale specifies howfast weighting factors decrease along the axis (wL decreasing from leftto right or wT decreasing from top to bottom), namely weighting factordecrement rate, and it is the same along x-axis (from left to right) andy-axis (from top to bottom) in current design. And 32 denotes theinitial weighting factors for the neighboring samples, and the initialweighting factor is also the top (left or top-left) weightings assignedto top-left sample in current CB, and the weighting factors ofneighboring samples in PDPC process should be equal to or less than thisinitial weighting factor.

For planar mode wTL=0, while for horizontal mode wTL=wT and for verticalmode wTL=wL. The PDPC weights can be calculated with adds and shiftsonly. The value of pred(x,y) can be computed in a single step using Eq.1.

FIG. 10 is a simplified block diagram 1000 in accordance withembodiments and shares additional context with respect to descriptionsherein regarding FIG. 3 . There is illustrated an input bitstream 1001provided to a video syntax parser 1001 and an output picture 1011 withone or more display resolutions configured depending on various metadataincluded with, for example, the input bitstream 1001 and may be providedto one or more displays.

As with parser 304, described in further detail here, the video syntaxparser 1002 provided processing, including handing of metadata, andprovides similar information to one or more of thedequantizer/inverse-transform unit(s) 1003, the intra predictor unit(s)1004, and the inter predictor (motion compensation) unit 1005 assimilarly described with respective units of FIG. 3 . The aggregator1006 provides, according to exemplary embodiments, output samples thatmay be subject to various loop filtering techniques in the in-loopfilter unit 1007 as with the loop filter 311 such as responsive to themetadata described above with respect to the input bitstream which mayalso be obtained during the decoding of one or more previous (indecoding order) parts of the coded picture or coded video sequence, aswell as responsive to previously reconstructed and loop-filtered samplevalues.

Herein, an RPR may enable a change of decoded picture spatialresolutions picture-by-picture within a coded video sequence (CVS), anda decoded picture, such as stored in a decoded picture buffer (DPB)1008, may be outputted for display via the up-sampler unit 1010 withrespect to converting a decoded picture to an output picture.

FIG. 11 is a simplified illustration 1100 of VUI parameter syntax andsuch flags described herein may be included such VUI parameter. inaccordance with embodiments and illustrates one or more algorithms withrespect to considering exemplary embodiments of VUI parameters which maybe used any of collectively and separately. One or more of such VUIparameters represents aspects of the metadata described above withrespect to FIG. 10 enabling an addressing of one or more differentrequirements, which are carrying an intention, such as a director'sintention, and leaving a freedom of a display for post processing, bysignaling any of a constant output picture size in VUI, for example asan informative metadata. According to embodiments, an end user's devicemay still have a freedom to choose the display picture resolution, whilealso being able to accept a director's suggestion, optionally, asdescribed herein.

For example, the illustration 1100 includes aconstant_output_pic_size_flag, which, according to exemplary embodiment,when equal to 1 specifies that any post-resampling process is applied toeach cropped output picture so that each resampled output picture shallhave the constant picture size, specified byconstant_output_pic_width_in_luma_samples andconstant_output_pic_height_in_luma_samples. In contrast, according toembodiments, a constant_output_pic_size_flag equal to 0 specifies that apost-resampling process may or may not be applied to each cropped outputpicture.

Further, the illustration 1100 includes aguided_constant_output_pic_size_present_flag, which, when equal to 1specifies that a both constant_output_pic_width_in_luma_samples and aconstant_output_pic_height_in_luma_samples are present in this VUI. Incontrast, according to embodiments, aguided_constant_output_pic_size_present_flag equal to 0 specifies thatboth or at least one of constant_output_pic_width_in_luma_samples andconstant_output_pic_height_in_luma_samples are not present in this VUI.

Further, the illustration 1100 includes one or moreconstant_output_pic_width_in_luma_samples value which specifies thewidth of each output picture after a post-resampling process in units ofluma samples. In contrast, when not present, the value ofconstant_output_pic_width_in_luma_samples is inferred to be equal topic_width_max_in_luma_samples in a SPS.

Further, the illustration 110 includes one or moreconstant_output_pic_height_in_luma_samples value which specifies theheight of each output picture after a post-resampling process in unitsof luma samples. In contrast, when not present, the value ofconstant_output_pic_height_in_luma_samples is inferred to be equal topic_height_max_in_luma_samples in SPS.

Therefore, according to exemplary embodiments, there is determining, inresponse to determining that the metadata comprises the at least oneflag, whether the metadata comprises a width value specifying the widthwith respect to a plurality of pictures, including the at least onepicture, and whether the metadata comprises a height value specifyingthe height with respect to the plurality of pictures. Further, accordingto exemplary embodiments, there is signaling, in response to determiningthat the metadata comprises the at least one of the width value and theheight value, at least one post-resampling process to maintain the atleast one of the width value and the height value for display of the atleast one picture by the display device described herein, and there isalso signaling, in response to determining that the metadata is absentthe width value and/or the height value, the at least onepost-resampling process to maintain the one or more corresponding one ofthe absent width value and/or the height value at a width and/or aheight respectively as indicated by a SPS of the video data.

According to exemplary embodiments, therefore, by inclusion of suchmetadata along with the processing described in FIG. 10 , an outputdisplay, such as a resolution, may be controlled according to an intenttransmitted along with the input bitstream 1001 as at least part of themetadata. Such control information may be included with the outputpicture 1011 as metadata and may direct a post-processing device to anyof only display the output picture 1011 in an output display resolutionas specified by the metadata as described when the flag values in FIG.11 are present and positive, and to provide an option to thepost-processing device to decide, such as via a user selection at thetime of entry of the data or predetermined or default, to select betweenwhether to output display resolution as specified by the metadata asdescribed when the flag values in FIG. 11 and whether to otherwiseoutput the display resolution as controlled by the post-processing ofthe output display device. As described herein, such indications may beprovided by one or more flags included as metadata with at least theinput bitstream 1001 and or the output picture 1011 output to a displaydevice.

Accordingly, by exemplary embodiments described herein, the technicalproblems noted above may be advantageously improved upon by one or moreof these technical solutions.

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media or by a specifically configured one or morehardware processors. For example, FIG. 12 shows a computer system 1200suitable for implementing certain embodiments of the disclosed subjectmatter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by computer central processing units (CPUs),Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 12 for computer system 1200 are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system 1200.

Computer system 1200 may include certain human interface input devices.Such a human interface input device may be responsive to input by one ormore human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard 1201, mouse 1202, trackpad 1203, touch screen1210, joystick 1205, microphone 1206, scanner 1208, camera 1207.

Computer system 1200 may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen 1210, or joystick 1205, but there can also be tactilefeedback devices that do not serve as input devices), audio outputdevices (such as: speakers 1209, headphones (not depicted)), visualoutput devices (such as screens 1210 to include CRT screens, LCDscreens, plasma screens, OLED screens, each with or without touch-screeninput capability, each with or without tactile feedback capability—someof which may be capable to output two dimensional visual output or morethan three dimensional output through means such as stereographicoutput; virtual-reality glasses (not depicted), holographic displays andsmoke tanks (not depicted)), and printers (not depicted).

Computer system 1200 can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW1220 with CD/DVD 1211 or the like media, thumb-drive 1222, removablehard drive or solid state drive 1223, legacy magnetic media such as tapeand floppy disc (not depicted), specialized ROM/ASIC/PLD based devicessuch as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system 1200 can also include interface 1299 to one or morecommunication networks 1298. Networks 1298 can for example be wireless,wireline, optical. Networks 1298 can further be local, wide-area,metropolitan, vehicular and industrial, real-time, delay-tolerant, andso on. Examples of networks 1298 include local area networks such asEthernet, wireless LANs, cellular networks to include GSM, 3G, 4G, 5G,LTE and the like, TV wireline or wireless wide area digital networks toinclude cable TV, satellite TV, and terrestrial broadcast TV, vehicularand industrial to include CANBus, and so forth. Certain networks 1298commonly require external network interface adapters that attached tocertain general-purpose data ports or peripheral buses (1250 and 1251)(such as, for example USB ports of the computer system 1200; others arecommonly integrated into the core of the computer system 1200 byattachment to a system bus as described below (for example Ethernetinterface into a PC computer system or cellular network interface into asmartphone computer system). Using any of these networks 1298, computersystem 1200 can communicate with other entities. Such communication canbe uni-directional, receive only (for example, broadcast TV),uni-directional send-only (for example CANbusto certain CANbus devices),or bi-directional, for example to other computer systems using local orwide area digital networks. Certain protocols and protocol stacks can beused on each of those networks and network interfaces as describedabove.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core 1240 of thecomputer system 1200.

The core 1240 can include one or more Central Processing Units (CPU)1241, Graphics Processing Units (GPU) 1242, a graphics adapter 1217,specialized programmable processing units in the form of FieldProgrammable Gate Areas (FPGA) 1243, hardware accelerators for certaintasks 1244, and so forth. These devices, along with Read-only memory(ROM) 1245, Random-access memory 1246, internal mass storage such asinternal non-user accessible hard drives, SSDs, and the like 1247, maybe connected through a system bus 1248. In some computer systems, thesystem bus 1248 can be accessible in the form of one or more physicalplugs to enable extensions by additional CPUs, GPU, and the like. Theperipheral devices can be attached either directly to the core's systembus 1248, or through a peripheral bus 1251. Architectures for aperipheral bus include PCI, USB, and the like.

CPUs 1241, GPUs 1242, FPGAs 1243, and accelerators 1244 can executecertain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM1245 or RAM 1246. Transitional data can be also be stored in RAM 1246,whereas permanent data can be stored for example, in the internal massstorage 1247. Fast storage and retrieval to any of the memory devicescan be enabled through the use of cache memory, that can be closelyassociated with one or more CPU 1241, GPU 1242, mass storage 1247, ROM1245, RAM 1246, and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture 1200, and specifically the core 1240 can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core 1240 that are of non-transitorynature, such as core-internal mass storage 1247 or ROM 1245. Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core 1240. A computer-readablemedium can include one or more memory devices or chips, according toparticular needs. The software can cause the core 1240 and specificallythe processors therein (including CPU, GPU, FPGA, and the like) toexecute particular processes or particular parts of particular processesdescribed herein, including defining data structures stored in RAM 1246and modifying such data structures according to the processes defined bythe software. In addition or as an alternative, the computer system canprovide functionality as a result of logic hardwired or otherwiseembodied in a circuit (for example: accelerator 1244), which can operatein place of or together with software to execute particular processes orparticular parts of particular processes described herein. Reference tosoftware can encompass logic, and vice versa, where appropriate.Reference to a computer-readable media can encompass a circuit (such asan integrated circuit (IC)) storing software for execution, a circuitembodying logic for execution, or both, where appropriate. The presentdisclosure encompasses any suitable combination of hardware andsoftware.

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

What is claimed is:
 1. A method for video coding performed by at leastone processor, the method comprising: acquiring metadata of video data;and determining whether, for any post-resampling process, each of aplurality of resampled output pictures is to have a constant picturesize based on the metadata specifying at least one of a width and aheight with respect to a plurality of pictures.
 2. The method for videodecoding according to claim 1, wherein the video data is in a versatilevideo coding (VVC) format.
 3. The method for video decoding according toclaim 2, determining whether each of the plurality of resampled outputpictures is to have the constant picture size is based on determiningwhether a component of the metadata comprises at least one flagsignaling at least one component of a picture size of at least onepicture of the video data.
 4. The method for video decoding according toclaim 3, wherein the component comprises at least one dimension of theat least one picture.
 5. The method for video decoding according toclaim 4, wherein the at least one dimension of the at least one picturecomprises units of luma samples.
 6. The method for video decodingaccording to claim 3, wherein the at least one flag specifies whether todisplay the at least one picture at the picture size according to avalue of the component that is present and indicated by the metadata. 7.The method for video decoding according to claim 6, wherein said anypost-resampling process is of cropped output pictures.
 8. The method forvideo decoding according to claim 1, further comprising: signaling thatsaid any post-resampling process is to maintain a width value at a valueindicated by a sequence parameter set of the video data.
 9. The methodfor video decoding according to claim 1, further comprising: signalingthat said any post-resampling process to maintain a height value at avalue indicated by a sequence parameter set of the video data.
 10. Themethod for video decoding according to claim 1, further comprising:determining that each of the resampled output pictures is to have theconstant picture size by checking the metadata for at least one flag ofa video usage information (VUI) parameter.
 11. An apparatus for videodecoding, the apparatus comprising: at least one memory configured tostore computer program code; at least one processor configured to accessthe computer program code and operate as instructed by the computerprogram code, the computer program code including: acquiring codeconfigured to cause the at least one processor to acquire metadata ofvideo data; and determining code configured to cause the at least oneprocessor to determine whether, for any post-resampling process, each ofa plurality of resampled output pictures is to have a constant picturesize based on the metadata specifying at least one of a width and aheight with respect to a plurality of pictures.
 12. The apparatus forvideo decoding according to claim 11, wherein the video data is in aversatile video coding (VVC) format.
 13. The apparatus for videodecoding according to claim 12, wherein the determining code is furtherconfigured to cause the at least one processor to determine whether eachof the plurality of resampled output pictures is to have the constantpicture size is based on determining whether a component of the metadatacomprises at least one flag signaling at least one component of apicture size of at least one picture of the video data
 14. The apparatusfor video decoding according to claim 13, wherein the componentcomprises at least one dimension of the at least one picture.
 15. Theapparatus for video decoding according to claim 14, wherein the at leastone dimension of the at least one picture comprises units of lumasamples.
 16. The apparatus for video decoding according to claim 13,wherein the at least one flag specifies whether to display the at leastone picture at the picture size according to a value of the componentthat is present and indicated by the metadata.
 17. The apparatus forvideo decoding according to claim 16, wherein said any post-resamplingprocess is of cropped output pictures.
 18. The apparatus for videodecoding according to claim 11, wherein the computer code furtherincludes signaling code configured to cause the at least one processorto signal that said any post-resampling process to maintain a widthvalue at a value indicated by a sequence parameter set of the videodata.
 19. The apparatus for video decoding according to claim 11,wherein the computer code further includes signaling code configured tocause the at least one processor to signal that said any post-resamplingprocess to maintain a height value at a value indicated by a sequenceparameter set of the video data.
 20. A non-transitory computer readablemedium storing a program configured to cause a computer to: acquiremetadata of video data; and determine whether, for any post-resamplingprocess, each of a plurality of resampled output pictures is to have aconstant picture size based on the metadata specifying at least one of awidth and a height with respect to a plurality of pictures.